This recipe is adapted from The Food of Spain and Portugal, by Elizabeth Ortiz. To make a heartier version of the soup, called caldo gallego, cook ingredients with a smoked ham hock; discard at the end. Stir in 1 to 2 cups white beans or garbanzo beans.
Fit a food mill with the medium sieve and force the potato mixture through into a bowl; alternatively, use a food processor or blender to puree.
* Mexican-style chorizo is usually fresh. Cook it thoroughly in a little olive oil and cool before slicing. The cured chorizo used in Spain or Portugal (chourico) does not need additional cooking.